It is commonly known in the art to use siccatives in coating dispersions such as paint dispersions. Typically, such siccatives contain metal soaps (metallic driers). Metal soaps may contain for example cobalt, lead, vanadium, or manganese but also soaps with other metals are available in the art. A previously preferred metal soap was cobalt soap due to its excellent performance with respect to drying time. Such metallic driers also contribute to reduced tackiness. Also, such driers are dissolved in suitable solvents, normally in aliphatic hydrocarbons which introduce up to 1 wt % volatile organic compounds to a coating dispersion or emulsion. Such driers, however, are hazardous to human health and may even be cancerogeneous.
The amount of drier used in waterborne systems is often used in higher concentrations than in solventborne systems to compensate for losses of primary driers (or active driers) such as cobalt, vanadium and manganese based driers.
While the solids portion of a coating dispersion adheres to the coated substrate, the solvent component if solventborne evaporates and causes environmental concern. The solvent materials are mostly volatile organic compounds (VOCS) that contribute to the creation of ozone (smog) in the lower atmosphere and are toxic to human health. Some solvents may also be classified as hazardous air pollutants (HAPs).
Alkyds are known to be used in coatings, in particular in paints. Such paints may be applied by means of solventborne and waterborne formulations. However, in particular waterborne paints may suffer from disadvantages such as low drying speed, drier incompatibility, through-drying, surface defects, poor hardness etc.
The present invention intends to provide an environmentally adapted coating composition which considerably reduces the metallic drier (active drier) content therein, or even completely omits the presence thereof in order to minimize evaporation of volatile organic compounds as a coating composition is drying on a substrate and hazardous metals, in particular cobalt, remaining in the formed coating. A further objective of the invention is to provide reduced yellowing of coatings.
The invention also intends to provide a composition which improves the vapour permeability of the film formed from e.g. a coating dispersion. A further objective is to reduce the drying time subsequent to application of such coating composition to a substrate. A further objective is to provide a reduced tack-free time. Another objective is to provide an improved dirt-pick up resistance to the film formed from the coating composition. A further objective of the invention is to improve the block resistance of the composition. A further objective is to provide an acceptable hardness to the coating. A further important objective of the present invention is to provide a stable coating composition which is not liable to gelling or precipitation. It is thus a requirement that the coating composition can be stored for a certain period of time, for example at least one year or at least two years without detrimental effects caused by separation or gelling. According to one embodiment, yet an objective is to provide an environmentally adapted system which is waterborne. According to yet one embodiment, the invention also intends to provide a composition having an improved hiding power.
The present invention intends to solve the problems referred to above.